The differentiation of pulpal cells into odontoblasts during pulpal healing will be studied in two model systems with a view to developing a biological method of pulp capping which will stimulate formation of sound dentine subjacent to the cap. A biological marker of differentiation, alkaline phosphatase is being characterized both histochemically and biochemically and is being used to follow differentiation of pulp derived fibroblasts in monolayer culture. Epithelial (dental organ) and mesenchymal co-cultures will be studied with electron microscopy. A three dimensional pulp culture system will be established which can be used to study interaction of pulp fibroblasts with surfaces of clinically usable materials. Several inert materials such as Millipore filter (0.45 micrometers and 0.1 micrometers - both sides of filter), cellophane, Teflon, isobutylcyanoacrylate and paper, will be tested in both the monolayer and three dimensional systems. Enzyme biochemistry and histochemistry as well as electron microscopic and histochemical techniques will be used to follow the interactions and differentiation of cells involved.